IDEAL

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© 2020 THE AUTHORS. ORTHOPAEDIC SURGERY PUBLISHED BY CHINESE ORTHOPAEDIC ASSOCIATION AND JOHN WILEY & SONS AUSTRALIA, LTD.
CLINICAL ARTICLE
Clinical Outcome of Remnant-Preserving and
I.D.E.A.L. Femoral Tunnel Technique for Anterior
Cruciate Ligament Reconstruction
Chao Su, MS1, Shi-da Kuang, MS1, Wei-jie Liu, MS1, Yu-sheng Li, MD1, Yi-lin Xiong, MD1, Xin Zhao, MS1,
Shu-guang Gao, MD1,2,3,4
1
Department of Orthopaedics, Xiangya Hospital and 4National Clinical Research Center of Geriatric Disorders, Xiangya Hospital, Central
South University, 2Hunan Key Laboratory of Joint Degeneration and Injury and 3Hunan Engineering Research Center of Osteoarthritis,
Changsha, China
Objective: To assess the clinical results of the remnant-preserving and I.D.E.A.L. femoral tunnel technique in the
arthroscopic treatment of anterior cruciate ligament (ACL) injuries.
Methods: This was a retrospective single-center, single-surgeon study reviewing data from November 2016 to March
2019. Based on our inclusion/exclusion criteria, a total of 31 patients (18 males, 13 females; mean age, 23.6 years)
who underwent arthroscopic ACL reconstruction with the remnant preservation and I.D.E.A.L. femoral tunnel technique
were recruited and had a minimum follow-up of 12 months. Clinical data and status of knee stability were recorded.
The International Knee Documentation Committee (IKDC) score, Lysholm score, and Tegner activity scale were collected both preoperatively and at a minimum of 1-year follow-up.
Results: Statistically significant differences were detected between the preoperative and postoperative values for
Lachman test and pivot-shift test (P < 0.01). The mean postoperative Lysholm score was 89.6 ± 9.4, whereas the mean
preoperative Lysholm score was 47.3 ± 12.8 (P < 0.01). The mean Tegner activity score was significantly higher at postoperative evaluation than at preoperative evaluation (6.5 ± 2.1 vs 2.6 ± 1.8; P < 0.01). The mean IKDC score was significantly improved from 49.5 ± 10.6 preoperatively to 88.2 ± 10.7 postoperatively (P < 0.01). No case of infection was
reported. No radiograph showed any joint space narrowing or degenerative change at the last postsurgical follow-up.
Conclusion: The anatomical remnant-preserving and I.D.E.A.L. femoral tunnel technique achieves a satisfactory clinical outcome and provides an effective option for the treatment of ACL injuries.
Key words: Anterior cruciate ligament; Arthroscopy; Femoral tunnel; Knee; Remnant preservation
Introduction
nterior cruciate ligament (ACL) injury is one of the
most common knee injuries; as estimated, there are
over 300,000 ACL injuries in the United States1. ACL reconstruction (ACLR) is one of the most commonly-used orthopaedic procedures that can help patients return to their
A
former activities with the support of postoperative rehabilitation, and it is reported that about 130,000 ACLR procedures
are operated each year in the United States1,2. Although satisfactory results have been published for the current ACLR
procedures, a review article reported poor outcomes and
symptomatic instability in a considerable subset of patients3.
Address for correspondence Shu-guang Gao, MD, Department of Orthopaedics, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha,
Hunan, China 410008 Tel: 0731-89753006; Fax: 0731-84327332; Email: 251469675@qq.com
Chao Su and Shi-da Kuang these authors equal contributors.
Disclosure: The authors declare that they have no competing interests.
Received 18 June 2020; accepted 2 August 2020
Orthopaedic Surgery 2020;12:1693–1702 • DOI: 10.1111/os.12791
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium,
provided the original work is properly cited.
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Several new approaches have been proposed to further
stabilize and improve the postoperative results of this technique3-6. One approach for improving the results of ACLR is
the remnant-preserving ACLR, which is featured with the
potential advantage of promoting faster graft revascularization and maturation to achieve better knee stability and clinical outcomes. Although positive results regarding this
approach have been reported by multiple clinical studies,
there are also researchers stating that no difference between
remnant preservation and standard ACLR was observed in
postoperative knee stability and clinical scores7,8. Another
approach for improving the results of ACLR is the correct
placement of femoral tunnel. Anatomical, histologic, isometric, biomechanical, and clinical data accumulated from more
than 4 decades collectively points to an optimal position for
the femoral tunnel within the femoral footprint9. This position can be summarized by the acronym I.D.E.A.L., which
means the ACL graft is Isometric, in the Direct fibers, Equidistant and Eccentric, Anatomic, and Low in tension9.
Despite being introduced in an article published as early as
5 years ago, the I.D.E.A.L. femoral tunnel technique has not
been widely adopted yet. This is possibly because the clinical
results of this technique have not been reported.
The aim of this study was to evaluate the clinical
results of the remnant-preserving and I.D.E.A.L. femoral
tunnel technique in ACLR, based on the hypothesis that the
remnant-preserving ACLR with the I.D.E.A.L. femoral tunnel
technique is an effective procedure.
Methods
Inclusion and Exclusion Criteria
The inclusion criterion were: (i) patients had subjective
instability and functional impairment confirmed by a positive Lachman test and/or pivot-shift test result; (ii) patients
had ACL lesions confirmed by magnetic resonance imaging;
(iii) patients had closed femoral and tibial diaphyses; (iv)
patients had no history of surgery on either knee; (v) patients
had no or minimal osteochondral degeneration on radiographic examination; (vi) patients who were scheduled to
undergo single-bundle ACLR using the remnant preservation
and I.D.E.A.L. femoral tunnel technique with a hamstring
autograft; (vii) patients had completed a clinical follow-up of
at least 12 months.
The exclusion criteria were: (i) patients without identifiable ligament tissue remaining; (ii) patients aged >50 years;
(iii) the affected knee suffered from moderate to severe
arthritis; (iv) patients who had previous knee surgery, rheumatological disorders, and associated malalignment (severe
valgus >7 or varus knee deviation >10 ); (v) patients with
combined ligament injuries.
Patient Information
This retrospective study was carried out upon receiving
approval from our institution’s ethical review board. We
included clinical outcomes of 31 patients who underwent the
SURGERY TECHNIQUE FOR ACL RECONSTRUCTION
TABLE 1 Characteristics of patients (n = 31)
Male/female sex, n (% male)
Age, mean ± SD (range), years
Laterality (right)
Body mass index, mean ± SD
(range), kg/m2
Time from injury to surgery,
mean ± SD (range), weeks
Concomitant procedures, n (%)
Meniscal repair
Meniscectomy
Surgical duration(min)
Follow-up (months)
18/13 (58.1)
23.6 ± 9.6 (18–47)
19 (61.3)
24.3 ± 4.0 (18.5–30.5)
12.6 ± 16.7 (1–96)
5 (16.1)
9 (29.0)
62 (40–90)
18.2 (12–36)
arthroscopic ACLR with the remnant preservation and
I.D.E.A.L. femoral tunnel technique alongside a clinical
review between November 2016 and March 2019 (Table 1).
The anterior drawer and Lachman tests were performed both
preoperatively and at the last follow-up. All operations were
performed by the same surgeon.
Surgical Technique
Anesthesia and Exposure
General anesthesia was executed while the patient was placed
in the supine position, with the affected side hanging down
to the knee joint level. A thigh tourniquet was typically used
to control bleeding and improve visualization. A routine
arthroscopic examination was performed using a probe with
a 30 oblique arthroscope at the anterolateral (AL) portal
and a probe in the anteromedial (AM) portal. The synovial
membrane, blot clots, and part of the infrapatellar fat pad
were removed at 90 knee flexion.
Graft Harvest and Preparation
The tendons were harvested through a 3-cm skin incision
over the upper medial tibial metaphysis. The semitendinosus
and gracilis tendons were harvested using the tendon stripper. A five-strand graft would be prepared if the tendon had
a minimum length as follows: 24 cm for the semitendinosus
tendon and 16 cm for the gracilis tendon. This was required
to prepare a five-strand hamstring graft with a minimum
length of 80 mm, given the need to triple the semitendinosus
tendon and double the gracilis tendon. This allowed for at
least 25 mm of the graft in the femoral tunnel, 30 mm inside
the joint, and at least 25 mm in the tibial tunnel. Usually an
8-mm (range, 7–9 mm) tunnel would allow passage of the
graft.
Femoral Tunnel Preparation
After checking the femoral-side footprint by arthroscopy
(through the AL portal), the footprint center was marked with
an electrocautery device passed through the AM portal. This
position can be described by the acronym I.D.E.A.L., which
refers to placing a femoral tunnel in a position that reproduces
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Fig. 1 Black circle (I.D.E.A.L. femoral tunnel) locates the ideal placement
of femoral tunnel in the single-bundle anterior cruciate ligament (ACL)
reconstruction. This position can be summarized by the acronym I.D.E.A.
L., which refers to placing a femoral tunnel in a position that reproduces
the Isometry of the native ACL, that covers the fibers of the Direct
insertion histologically, that is Eccentrically located in the anterior (high)
and proximal (deep) region of the footprint, that is Anatomical (within the
footprint), and that replicates the Low tension-flexion pattern of the native
Fig. 2 The intraoperative check for correct positioning of the femoral
ACL throughout the range of flexion and extension.
of the notch within the green zone and far enough posterior to position
the femoral tunnel with a ≤2 mm tunnel backwall.
the Isometry of the native ACL, that covers the fibers of the
Direct insertion histologically, that is Eccentrically located in
the anterior (high) and proximal (deep) region of the footprint,
that is Anatomical (within the footprint), and that replicates
the Low tension-flexion pattern of the native ACL throughout
the range of flexion and extension (Fig. 1).
The intraoperative check for correct positioning of the
femoral tunnel is to place the guide wire equidistant from
the top to the bottom of the notch within the green zone
and far enough posterior to position the femoral tunnel with
a ≤2 mm tunnel backwall10 (Fig. 2). The femoral tunnel in
single-bundle ACLR was drilled through the AM portal
using a 6 mm Smith & Nephew offset femoral aimer. The
knee was bent to 90 in order to place the guide 6 mm anterior to the posterior edge of the intercondylar notch. Once
the guide was in place, the knee was slowly flexed to 120 or
more as permissible to ensure a more anterior directed tunnel for avoiding posterior blowout, and to provide an adequate tunnel length and safe exit for the guidewire on the
lateral aspect of the thigh. A 2.4-mm drill tip guide wire was
advanced through the offset femoral guide and drilled
through the femur until the guide wire “broke” through the
lateral femoral cortex. A 4.5-mm drill was advanced over the
passing pin to break the lateral femoral cortex. An endoscopic cannulated drill bit that matched the graft diameter
(7–9 mm) was selected and used to produce the femoral
socket with a 20–25 mm depth. The femoral socket was
placed as close to the posterior aspect of the notch as
possible, making sure that 1–2 mm of the bone would
remain as a posterior wall for the femoral socket, which indicates the I.D.E.A.L. placement (Fig. 2).
tunnel is to place the guide wire equidistant from the top to the bottom
Tibial Tunnel Preparation
A tibial drill guide was inserted through a standard
anteromedial portal and positioned in the center of the
remaining ACL footprint (Fig. 3). The guidewire was
advanced into the joint and carefully directed to be in line
with the ACL remnant. When the optimal position was
achieved, the guide pin was then over-drilled using a cannulated reamer of 7-mm, 8-mm, or 9-mm diameter to make a
tibial tunnel of the same diameter as the graft. The reamer
must be advanced cautiously to minimize the chance of
injury to the residual remnant at the intra-articular margin
of the tibial tunnel. Penetration should stop at the base of
the stump. The tunnel ends were then rounded off with an
abrasion burr to reduce graft abrasion.
Passage and Fixation of the Graft
The passing and tensioning sutures were passed through the
tibial and femoral tunnel using a guide pin. The TightRope
button was passed through the femoral tunnel using the
passing sutures and flipped on the lateral cortex of the distal
femur by the distal traction applied to the graft. The tensioning sutures were pulled slowly. Arthroscopic visualization
confirmed that the previous mark on the graft was flushed
with the outlet of the femoral tunnel, indicating full insertion
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Fig. 3 The guide pin passes through the center of the tibial remnant.
of the graft into the femoral tunnel. While maintaining tension on the graft, the screws were inserted with the knee
being flexed at 20 . The graft impingement was assessed
intraoperatively with the knee in full extension. For more
details of the full procedures carried out in this study, please
refer to our typical cases (Figs 4,5,6).
Postoperative Management
Quadricep exercises and straight-leg raises were performed
immediately upon completion of the operation. Full weightbearing was permitted immediately as tolerated. The knee was
immobilized in full extension using an ACL limited-motion
brace for 1 week after the operation; then, range-of-motion
exercises would start gradually. The 90 motion and 135
motions were allowed 4 weeks and 6 weeks after surgery,
respectively. Meanwhile, at 6 weeks postoperatively, the patients
would advance to the standard ACL rehabilitation protocol with
the purpose to return to physical activities at 6 months. The
brace was then removed 3 months after surgery. Then, at 3 and
6 months postoperatively, straight-line running and direction
changing while running, respectively, were allowed.
Outcome Measures
Clinical data and status of knee stability were recorded accordingly. The International Knee Documentation Committee
(IKDC) score, Lysholm score, and Tegner activity scale were collected both preoperatively and at a minimum of 1-year follow-up.
The IKDC evaluation form was used to detect the
improvement or deterioration in symptoms, function, and
sports activities. The response to each item was scored using an
ordinal method. The most recent version had assigned scores
for each possible response printed on the questionnaire. Scores
for each item were added together to obtain a total score
(excluding item 10a). The total score was calculated as (sum of
items)/(maximum possible score) × 100, to give a total score of
100. An online scoring sheet was available that provides a
patient’s raw score and percentile score. The item regarding
knee function prior to knee injury was not included in the total
score. Possible score range was 0–100, where 100 = no limitation
with daily or sporting activities and the absence of symptoms.
The Tegner activity scale was used to provide a standardized method of grading work and sporting activities. A
score of 10 is assigned based on the level of activity that the
patient selects. A score of 0 represents sick leave or disability
pension because of knee problems, whereas a score of 10 corresponds to participation in national and international elite
competitive sports and a score >6 can only be achieved if the
person participates in recreational or competitive sport.
The Lysholm Scale is a patient-reported outcome measure (PROM) for evaluating knee function, which consists of
eight items: pain (25 points), instability (25), locking (15),
swelling (10), limp (5), stair climbing (10), squatting (5), and
need for support (5). The total score for a respondent is the
sum of the eight items, which may range from 0 to 100. A
higher score indicates a better outcome.
Statistical Analysis
Statistical analyses were performed using SPSS software version 22.0 (SPSS Inc., Chicago, IL, USA). The paired t-test
was conducted to evaluate the differences in scores between
preoperative and postoperative measurements. A P value
<0.05 was considered as statistically significant.
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Fig. 4 (A) MRI showed that ACL was broken and formed a low flat shape in the joint. (B) Arthroscopic rupture of ACL was observed, and the scar on
posterior cruciate ligament (PCL) had healed. (C) After marking the I.D.E.A.L. point with a plasma knife, the Kirschner wire was positioned through the
ACL femoral locator for femoral drilling. (D) Intraoperative check of the position of the thick femoral bone tunnel. (E) A tibial drill guide was inserted
through a standard anteromedial portal and positioned at the center of the remaining ACL footprint. (F) The graft was fixed through the tibial and
femoral bone tunnel in order to observe it under arthroscopy. It was found that the graft just passed the center of the ACL stump and the surface was
covered by the fibers of ACL remnant. (G,H) Postoperative anteroposterior and lateral plain radiographs showed the correct position of the TightRope
button. (I) 3D CT scan reconstruction with a tibial tunnel position. (J) 3D CT scan reconstruction with a femoral tunnel position.
Results
Demographic Characteristics and Follow-up
Thirty-one patients were included, consisting of 18 men
(58%) and 13 women (42%). The mean age was 23.6 years
(18–47 years), and the mean follow-up was 18.2 months
(12–36 months). Of the 31 patients, 14 had a concurrent
meniscus tear.
There were three patients who showed extension limitation preoperatively. The medial meniscus showed a locked
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Fig. 5 (A) MRI showed that ACL was broken, and the fiber of ACL was not continuous in the joint. (B) ACL rupture could be observed under
arthroscopy, and ACL remnant showed cyclops lesion in the knee. (C) The position of the I.D.E.A.L. tunnel after the creation of the femoral tunnel.
(D) The position of Kirschner wire in the tibial tunnel was located at the center of ACL remnant. (E) The shaver could reach the femoral tunnel through
the tibial tunnel. It can be seen that the correspondence between the positions of the two tunnels in the joint was appropriate. (F) The graft of
reconstructed ACL was well positioned in the joint. (G,H) Postoperative anteroposterior and lateral plain radiographs showed that the TightRope
button was flipped on the lateral cortex of the distal femur by the distal traction applied to the graft. (I) The tibial tunnel (sagittal CT image) was
located at the anatomic position. (J) 3D CT scan reconstruction with a femoral tunnel position.
bucket-handle tear in two of them, and they had 10 of
extension limitation. One patient with a lateral meniscus tear
also had 20 of extension limitation. A partial meniscectomy
was performed in six medial and three lateral menisci, and
meniscal repair was performed in three medial and two lateral menisci. Postoperatively, all of them showed full extension of the knees. The second-look arthroscopic examination
was not performed in any patients.
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Fig. 6 (A) MRI of the right knee showed rupture of the femoral end of ACL. (B) A routine arthroscopic examination was performed using a probe with a
30 oblique arthroscope in the anterolateral (AL) portal and another probe in the anteromedial (AM) portal. ACL avulsion from femoral insertion was
observed. (C) Position of the I.D.E.A.L. femoral tunnel (arthroscopic view). A guide PDS was placed through the femoral bone tunnel. (D) The tibial tunnel
(the position of the Kirschner wire) was located at the center of ACL remnant. (E) The position of ACL graft in the joint after fixation through the tibial and
femoral tunnels. (F) The ACL graft and ACL remnant were sutured together with PDS suture. (G,H) Postoperative anteroposterior and lateral plain
radiographs showed the correct position of the titanium plate. (I) Volumetrically rendered image from sagittal computed tomography taken after primary
ACLR showed that the tunnels were located at the anatomic position. (J) 3D CT scan reconstruction with a femoral tunnel position. (K) 3D CT scan
reconstruction with a tibial tunnel position.
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TABLE 2 Anterior knee stability on physical examination as
reported by the subjective grading of Lachman and Pivot-Shift
maneuvers [n(%)]
Test
Lachman
Preoperative
Postoperative
Pivot Shift
Preoperative
Postoperative
0
1
2
3
0 (0)
29 (93.5)
1 (3.2)
2(6.5)
5 16.1)
0 (0)
25 (80.6)
0 (0)
0 (0)
28(90.3)
0 (0)
2 (6.5)
6 (19.4)
1 (3.2)
25 (80.6)
0 (0)
General Results
The mean time from injury to surgery was 12.6 weeks
(range, 1–96 weeks). The surgical duration was 40–90 min
with a mean of 62 min, and the average blood loss was
15 mL (range, 10–20 mL). The average total duration of hospital stay was 3.2 days (range, 1 to 7 days). The average post
hospital stay for the arthroscopic surgery group was 2.5 days
(range, 1 to 6 days). No radiograph showed joint space
narrowing or degenerative change at the last postsurgical
follow-up.
Ligament Laxity
Frequencies of Lachman and pivot-shift testing grades for
preoperative and postoperative conditions are presented in
Table 2. The Lachman test was negative in 29 patients, one
plus in two in the postoperative conditions. The Pivot Shift
test was negative in 28 patients, one plus in two and two plus
in one in the postoperative conditions. Statistically significant
differences were observed between the preoperative and postoperative values for Lachman test and pivot-shift
test (P < 0.01).
Lysholm Evaluation
The mean postoperative Lysholm score was 89.6 ± 9.4
(Table 3), whereas the mean preoperative Lysholm score was
47.3 ± 12.8 (P < 0.01). For the general grading results, 81%
were good and 19% were fair.
Tegner Rating
Preoperative and postoperative Tegner scores were used to
indicate the patients’ capability of returning to their preinjury life/work and activity level (Table 3). The mean
Tegner activity score was significantly higher at the postoperative evaluation than at the preoperative evaluation
(6.5 ± 2.1 vs 2.6 ± 1.8; P < 0.01).
TABLE 3 Mean clinical scores (and standard deviations) on
preoperative and postoperative evaluations
Parameter
Preoperative
Postoperative
P value
Lysholm score
Tegner scores
IKDC subjective score
47.3 ± 12.8
2.6 ± 1.8
49.5 ± 10.6
89.6 ± 9.4
6.5 ± 2.1
88.2 ± 10.7
< 0.01
< 0.01
< 0.01
SURGERY TECHNIQUE FOR ACL RECONSTRUCTION
IKDC Subjective Score
The mean IKDC score (Table 3) was significantly improved
from 49.5 ± 10.6 preoperatively to 88.2 ± 10.7 postoperatively (P < 0.01).
Complication
One patient experienced the wound problem (fat liquefaction), which was resolved following treatment with oral antibiotics. One case of tourniquet complication was indicated
by skin blisters. No case of DVT or iatrogenic neurovascular
compromise was identified. No wound infection or
neurovascular injury was observed.
Discussions
ince the results of ACLR were affected by a wide range
of variables, the optimal techniques are still being pursued. No previous clinical studies have been reported concerning the outcome of isolated remnant-preserving ACLR
with the I.D.E.A.L. femoral tunnel technique. Our study
showed that ACLR with the remnant preservation and I.D.E.
A.L. femoral tunnel technique was a good surgical option
delivering satisfactory clinical results.
S
Advantages and Pearls of Remnant Preservation
First of all, even though an ACL remnant that bridges the
femur and tibia should be debrided to create the femoral and
tibial tunnels in standard ACLR, it has been proven that
these remnants can conserve the neuroreceptors and mechanoreceptors, which is beneficial to the joint position sense
after surgery11,12. Secondly, as far as the revascularization of
the grafted tendon is concerned, an ACL remnant with
abundant vascularity can exert a favorable effect allowing
swifter “ligamentization” of the graft13,14. A previous study
reported that the scar pattern of the tibial stump could be
classified into four types and at least 50% of the patients with
ACL injury had part of the remnant tissue, even though the
amount of remnant tissue might depend on the time from
injury to surgery15. Thirdly, the preserved proprioceptive
nerve fibers in the distal tibial stump would reinnervate the
reconstructed ACL. Georgoulis et al.16 suggested that the
presence of a proprioceptive mechanoreceptor in the remnants of the ruptured ACL might be a possible source of
reinnervation of the ACL autograft. Distinguishing the effect
of remnant preservation on the restoration of proprioception
is difficult, and therefore, more sensitive and specific
equipment or systems need to be developed to assess the
proprioceptive function of the knee.
At present, the advantages of remnant preservation are
difficult to demonstrate using clinical scores (e.g., Lysholm
knee score, HSS score, or IKDC score) or physical examination (pivot-shift or Lachman test). It is believed that the theoretic advantages in revascularization, ligamentization, graft
incorporation, and preservation and reinnervation of mechanoreceptors can be proven by the long-term failure rate or
evaluation of proprioception. Lee et al.12 suggested that the
remnant-preserving technique in ACLR yielded better
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proprioceptive and functional outcomes and might help
achieve better postoperative patient satisfaction. Second-look
arthroscopy is a good tool for evaluating graft healing by
observing synovial coverage, graft tension, and the presence
of partial tears and impingement. Kondo et al.17 reported
that the arthroscopic evaluations in remnant-preserving
ACLR were significantly better than those in standard ACLR,
which could severely affect the postoperative knee stability.
Perhaps with a longer follow-up, some differences would
emerge in terms of re-rupture rate, subjective results, and
posttraumatic arthritis. Therefore, more randomized
controlled and long-term follow-up studies are needed to
confirm our hypothesis.
The remnant amount and the minimal injury to residual remnant are important factors in promoting the restoration of proprioceptive function. Muneta et al.18 compared
the clinical outcomes of three groups (classified according to
the remnant volume: ≤30%, 35%–55%, and ≥60%) and
found that the remnant volume was weakly correlated with
the postoperative outcome. On the other hand, Nakayama
et al.19 indicated that a large remnant might increase the
incidence of cyclops lesions and extension loss. In this study,
the length of the stump was properly preserved during the
operation; meanwhile, reaming was stopped at the base of
the remnant for minimal injury to the residual remnant.
Roof impingement with knee extension by scarring the graft
in the anterior intercondylar area (cyclops lesion) and anterior placement of the tibial tunnel can be prevented because
the tibial tunnel is positioned within the boundary of the
normal ACL remnant and surrounded by the remnant tissue.
The tibial remnant leaves no definite gap at the exit point of
the tunnel and prevents synovial fluid from tracking along
the graft. For these reasons, we believe that our technique
can well prevent tibial tunnel enlargement.
Advantages and Pearls of I.D.E.A.L. Femoral Tunnel
Technique
Anatomic femoral tunnel placement such that the ACLR
graft lies within the native ACL femoral attachment site and
has been shown to better restore anterior tibial translation,
rotational stability, and normal knee kinematics20–22. Clinical
studies have demonstrated that the most common technical
error resulting in instability or graft failure after ACLR is
nonanatomic graft placement and that the nonanatomic femoral tunnel position is closely correlated with poorer clinical
outcome scores23,24. Previous studies have reported that the
femoral socket is localized in the center of the entire footprint with a single-bundle technique and the sockets are created in the centrums of both the AM and PL bundles with a
DB technique20–24. However, in light of the discrepancy
between the size of the femoral footprint and the
mid-substance of the native ACL, it seems reasonable that
optimizing the position of the ACL femoral tunnel may be
more complex than simply centralizing the tunnel within the
footprint or attempting to maximize the footprint coverage.
According to Pearle9, the acronym I.D.E.A.L. reminds
SURGERY TECHNIQUE FOR ACL RECONSTRUCTION
surgeons to place the ACL graft in a femoral tunnel position
that reproduces Isometry of native ACL, that covers fibers of
Direct insertion, that is Eccentrically located in anterior
(high) and proximal (deep) region of footprint, that is Anatomical (within femoral footprint), and that replicates Low
tension-flexion pattern of native ACL throughout the range
of flexion and extension.
The intraoperative check for the correct positioning of
the femoral tunnel is to place the guide wire equidistant from
the top to the bottom of the notch within the green zone
and far enough posterior to position the femoral tunnel with
a ≤2 mm tunnel backwall10 (Fig. 2). Centering the femoral
guide wire in the green zone has the advantages of setting
the graft length isometrically, centering the graft in the direct
fibers of the origin of the native ACL anatomically, and
restoring low graft tension, which are associated with high
function, full motion, and high stability25. The advantage of
the green zone with the I.D.E.A.L. philosophy lies in that it
enables an anterior medial or transtibial drilling technique
while providing the ability to consistently place the tunnel
within the green zone and allows a small amount of latitude
in order to support the individuality of the patient’s anatomy
and notch. However, the achieved tunnel position for transtibial drillers was found to be higher in the intercondylar
notch than that for other drilling techniques (outside-in and
AM portal)26. In this study, the use of an AM-portal ACLR
technique could initially mark the tunnel position with an
electrocautery device and then verify this position by
switching to the AM portal. The 6-mm offset femoral aimer
used in the operation could control the distance of the
femoral tunnel to the posterior backwall.
Limitations
Several limitations of the present study deserve comments.
Firstly, our analysis was limited by the small number of cases
and non-comparative single-arm reports of surgical results.
More patients are expected to further validate our findings
and conclusions. Data of comparison relative to the singlebundle ACLR with remnant preservation or the standard
ACLR is needed. Secondly, another drawback of this study
was that the parameters of magnetic resonance imaging
(MRI) or computed tomography (CT) were not evaluated.
Thirdly, the mean term of follow-up was relatively short. It
is critical to include subjects with longer terms of follow-up
in order to better evaluate growth disturbances. Lastly, scientific research should be carried out to prove the benefit of
the remnant preserving technique.
Conclusions
n conclusion, our anatomical remnant-preserving and
I.D.E.A.L. femoral tunnel technique is an easy-to-operate
and effective method for the treatment of ACL injuries, with
excellent postoperative stability and clinical results.
I
1702
ORTHOPAEDIC SURGERY
VOLUME 12 • NUMBER 6 • DECEMBER, 2020
Acknowledgements
his work was supported by the National Natural Science
Foundation of China (No. 81672225), the Key Research
and Development Program of Hunan Province
T
SURGERY TECHNIQUE FOR ACL RECONSTRUCTION
(2018SK2075), the Xiangya Clinical Big Data System
Construction Project of Central South University (No. 45),
and the Clinical Scientific Research Foundation of Xiangya
Hospital, Central South University (2015 L01).
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